1. Field of the Invention
This invention relates to a printer and, more particularly, to a printer into which plural extension memories can be installed.
2. Description of Related Art
In many companies, personal computers or work stations have been recently introduced in association with the development of office automation. At the same time, these computers are connected to high-speed printers, such as laser printers, dot printers or the like, through the same cable used to configure a network system in which desired print data stored in the computers are transmitted to enable print processing using a desired printer.
In general, a ROM and a RAM are provided in a control device for each printer. The ROM is stored with font data on characters, symbols, etc. and various control programs. The RAM is equipped with a memory for storing received data, a font data memory for storing special font data that is not stored in the ROM and an image data memory for converting received print data to dot-pattern image data and storing it.
The RAM in the control device of the printer is generally designed to have such a memory capacity as to store the received data and the font data by only a predetermined data amount. However, recently large amounts of font data are required to be received and stored into the RAM to improve print efficiency. Thus, the set memory capacity of the RAM is too insufficient to meet this requirement. In view of the foregoing, a printer has been employed that has plural memory-installing slots into which extension memories having desired memory capacity are detachably installed and that are connected to the control device. That is, when the memory capacity of a printer is required to be extended, one or a plural extension memories bought separately from the printer's manufacturer or another manufacturer are installed into any of the plural memory-installing slots. Whereby, the memory capacity of the printer can be easily extended.
In a printer in which extension memories can be installed, the control device thereof is generally equipped with an address conversion circuit to simplify the address management of the extension memories. To simplify the circuit construction of the address conversion circuit and reduce the cost thereof, effective extension conditions are required when one or a plural extension memories are extended to all or some of the plural memory-installing slots. One extension condition is that the extension memories are successively installed from a first memory-installing slot. Another extension condition is that the extension memories are successively installed from the memory of minimum memory capacity in order of first, second, third, . . ., n-th memory-installing slots when the extension memories have different memory capacities, etc.
As described above, the memory capacity of the RAM can be easily extended by installing desired extension memories into the memory-installing slots. However, if an installing condition of these extension memories does not meet the above extension conditions, that is, when a user installs the extension memories into the memory-installing slots in noncompliance with the extension conditions, a memory error would occur, and the data reception and printing operations could not be carried out. In this case, the user must refer to a manual on the correct extension states (conditions) or, in the worst case, contact the manufacturer. Thus, implementing extension memories is complicated.